Nearly 500 law enforcement officials, aided by SWAT teams, made their way to the scene and immediately began scanning the area.

Two hours after the first shot was fired and still no sign of a gunman, law enforcement officials began to evacuate the mall.

"We go store by store, room by room, and that takes awhile," Jim Tedesco of the Paramus Office of Emergency Management said.

With more than two million square feet of retail space, New Jersey's largest mall was kept on lockdown as evacuations continued slowly throughout the night.

Paramus Mayor Richard LaBarbiera, said overnight, "If you have a loved one here, everybody is not only fine, but they're in great hands.

Just after 3 a.m. Shoop's body was discovered in a remote construction area on the mall grounds. Earlier, police had uncovered a note written by Shoop at the family home.

John Molinelli, Bergen County prosecutor, said: "I don't know, as I stand here, whether his motive was to injure anyone, I can't say that right now. But I do not believe that Mr. Shoop thought that he would come out of here this evening alive."

At some point, a family member of Shoop's called police and provided information that ultimately helped police locate Shoop's body. The mall remains closed.

Watch Elaine Quijano's full report above.

Mall officials have come to the realization that this is a phenomenon that's not going away -- and they're focusing on the issue "more and more," CBS News senior correspondent John Miller, a former assistant FBI director, explained on "CBS This Morning."

For more with Miller, watch his full analysis below.

Inside mall, police prep for active shooter situations

Some malls, such as Westfield Mall, Miller said, have developed an active shooter program for their security. The Israeli-owned company is "very focused on this," Miller said. "Part of their plan is a lockdown of the security command posts so that they can follow the events using video cameras and feed intelligence out," Miller said. "The other part is that security people respond out to the rally point where police will respond with something interesting. A couple of mall security radios so they can begin to communicate with people inside who may be guards who are hiding or trapped with other customers or who may have a vantage point. And the third thing is that they respond with a full floor plan of the location. And this has been drilled into every security person's head. Not to think about it, just do it."

The question going forward is command and control of these incidents, Miller added. "If you're a town like Paramus PD, they're well practiced this. Or a small place or large place, how do you execute the police function there? ... This is something that law enforcement is focused on because it keeps happening again and again. Part of it is the tactics. And the other part of the discussion is why is this happening? Why is it happening more?"